Aerobic Biodegradation Studies of Nonylphenol Ethoxylates in River Water Using Liquid Chromatography−Electrospray Tandem Mass Spectrometry

Abstract

The aerobic biodegradation of nonylphenol ethoxylates (A9PEO) was kinetically investigated in a laboratory-scale bioreactor filled with riverwater, spiked at a concentration of 10 mg L(-1) nonionic surfactants. Analyses of the samples applying liquid chromatography-electrospray mass spectrometry (LC-ES-MS) after solid-phase enrichment revealed a relatively fast primary degradation of A9PEO with >99% degradation observed after 4 days. Contrary to the generally proposed degradation pathway of EO chain shortening, it could be shown that the initiating step of the degradation is omega-carboxylation of the individual ethoxylate chains: metabolites with long carboxylated EO chains are identified (A9PEC). Further degradation proceeds gradually into short-chain carboxylated EO with the most abundant species being AgPE2C. The oxidation of the nonyl chain proceeds concomitantly with this degradation, leading to metabolites having both a carboxylated ethoxylate and an alkyl chain of varying lengths (CAPEC). The identity of the CAPEC metabolites was confirmed by the fragmentation pattern obtained with LC-ES-MS/MS. Both A9PEC and CAPEC metabolites are still present in the bioreactor after 31 days. In the aerobic degradation pathway, A9PEO2 is formed only to a minor extent and is even further degraded in several days. The endocrine disruptor nonylphenol was not found as a metabolite in this study.

Removal of Endocrine Disrupting Compounds During Conventional Wastewater Treatment

“…The very low levels of NP1EO and NP2EO in all samples appear to be consistent with the biodegradation pathway suggested by Jonkers et al [12] in which aerobic breakdown occurs via the carboxylic acid, then subsequent loss of the ethoxylate moiety and finally oxidation of the alkyl chain. Formation of NP2EO under aerobic conditions would appear to be a minor degradation route.…”

Modelling the fate of nonylphenolic compounds in the Seine River — part 2: Assessing the impact of global change on daily concentrations

“…13 4-NP mainly originates from the biodegradation of non-ionic surfactants nonylphenol polyethoxylate (NPnEO) 14 through anaerobic (John and White, 1998) or aerobic (Jonkers et al, 2001) processes. NPnEO are used in a large 15 range of domestic and industrial detergents, as emulsifier or wetting agents with a world annual consumption of 16 500,000 tons in 2000 (Ying et al, 2002).…”

Degradation pathways of low-ethoxylated nonylphenols by isolated bacteria using an improved method

“…In comparison with their mother molecules, however, information regarding the fates of low-ethoxylated NPEOs is still very limited. It is not clear, for example, why low-ethoxylated CAPECs, the metabolites with oxidized alkyl and ethoxy side chains, accumulate in the environment as a result of NPEO biotransformation (Ahel et al 1994;Di Corcia et al 1998;Jonkers et al 2001;.…”